This paper presents a decision making approach based on data envelopment analysis (DEA) for determining the most efficient number of operators and the efficient measurement of labor assignment in cellular manufacturing system (CMS). The DEA approach is performed by employing the average lead time, the average operator utilization as the output variables and using the number of operators, transfer batch size, demand level as the input variables. Both inputs and outputs are procured by means of simulation of CMS. The objective is to determine the labor assignment in CMS environment. (C) 2004 Elsevier B.V. All rights reserved.